1. Field of the Invention
This invention relates to the manufacture of prosthetic and orthotic devices and, in particular, to a fabrication assembly useful for aligning the components of such devices during fabrication, and to a casting apparatus for making molds from which prosthetic components can be made.
Prosthetic and orthotic devices often comprise articulated components that must be properly aligned so that their movement conforms to the shape and movement mechanics of the wearer's body. For example, a prosthetic knee joint provides a pivoting motion between upper leg and lower leg components and the plane defined by the pivoting movement may have to be fixed at a particular angle with respect to the wearer's sagittal plane to maximize the comfort and ease of use of the prosthetic device. Similarly, in a prosthetic device for an above-knee amputee, the foot may have to be disposed at a suitable angle relative to the direction of travel and the leg prosthesis may have to conform to a wearer's flexion contracture, if any, and any indicated adduction or abduction contracture angles. To facilitate assembly of the device that conforms to the wearer's needs, the components of the device must be held in proper alignment while they are interconnected. The alignment criteria, e.g., height, angle, rotation, lateral displacement, etc., are derived from the wearer using anatomical references. For example, the alignment criteria for leg prostheses are typically reported with reference to the wearer's TKA (Trochanter-Knee-Ankle) reference line and/or the Ischium-Knee Center-Heel line in their respective planes. Conventionally, a technician employs a fabrication assembly comprising a vertical or horizontal mast and a plurality of clamps mounted on the mast for holding the various components of the prosthetic or orthotic device during the assembly process. There is a variety of commercially available fabrication assemblies of this kind.
2. Related Art
One prior art fabrication apparatus is sold under the tradename Hosmer Vertical Fabricating Jig VFJ-100. The Hosmer apparatus comprises a rod-like, vertically oriented mast on which a plurality of clamps is secured. The clamps can be moved vertically on the mast and serve to slidably receive horizontally disposed support arms that hold various tooling modules useful for engaging components of prosthetic or orthotic devices. The mast of the Hosmer apparatus is vertically slotted so that clamps can easily be aligned to dispose the horizontal support arms in a common, vertically oriented plane. Each support arm extends from a clamp to a fixed distance from the mast and has a rotational orientation within the clamp. To vary either the distance from a tooling module on a support arm to the mast or the rotational orientation of the module, it is necessary to loosen the clamp. In so doing, both the rotational orientation and distance attributes are released. Therefore, both attributes must be carefully measured after each time the clamp is re-tightened. Further, the mast, clamp and support arms of the Hosmer apparatus only permit the adjustment of two alignment criteria for prosthetic device components secured thereto: linear distance from the mast and rotational orientation relative to the mast. Accordingly, if it is necessary that one tooling module be laterally displaced relative to another, all that can be done using the Hosmer apparatus is to rotate the support arm holding the tooling module to be moved. However, this motion imposes a rotation on the tooling module that may be unwanted. Stated differently, if the mast is viewed as corresponding to the vertical axis of the patient's body (i.e., as corresponding to the intersection of the frontal and sagittal planes) and if the support arms are viewed as extending forward from the patient's body, the Hosmer apparatus does not provide for true medial-lateral movement. One support arm on the Hosmer apparatus is slotted so that it can be moved horizontally without losing its rotational orientation in the clamp, but it carries a tooling module attached thereto by a ball joint. Clearly, after loosening the ball joint to reposition a component secured in the tooling module, all rotational and angular orientations of the component in the tooling module must be checked before re-tightening the ball joint.